pcsx2/common/Threading.h

255 lines
8.1 KiB
C++

// SPDX-FileCopyrightText: 2002-2024 PCSX2 Dev Team
// SPDX-License-Identifier: GPL-3.0+
#pragma once
#include "common/Pcsx2Defs.h"
#if defined(__APPLE__)
#include <mach/semaphore.h>
#elif !defined(_WIN32)
#include <semaphore.h>
#endif
#include <atomic>
#include <functional>
namespace Threading
{
// --------------------------------------------------------------------------------------
// Platform Specific External APIs
// --------------------------------------------------------------------------------------
// The following set of documented functions have Linux/Win32 specific implementations,
// which are found in WinThreads.cpp and LnxThreads.cpp
extern u64 GetThreadCpuTime();
extern u64 GetThreadTicksPerSecond();
/// Set the name of the current thread
extern void SetNameOfCurrentThread(const char* name);
// Releases a timeslice to other threads.
extern void Timeslice();
// For use in spin/wait loops.
extern void SpinWait();
// Optional implementation to enable hires thread/process scheduler for the operating system.
// Needed by Windows, but might not be relevant to other platforms.
extern void EnableHiresScheduler();
extern void DisableHiresScheduler();
// sleeps the current thread for the given number of milliseconds.
extern void Sleep(int ms);
// sleeps the current thread until the specified time point, or later.
extern void SleepUntil(u64 ticks);
// --------------------------------------------------------------------------------------
// ThreadHandle
// --------------------------------------------------------------------------------------
// Abstracts an OS's handle to a thread, closing the handle when necessary. Currently,
// only used for getting the CPU time for a thread.
//
class ThreadHandle
{
public:
ThreadHandle();
ThreadHandle(ThreadHandle&& handle);
ThreadHandle(const ThreadHandle& handle);
~ThreadHandle();
/// Returns a new handle for the calling thread.
static ThreadHandle GetForCallingThread();
ThreadHandle& operator=(ThreadHandle&& handle);
ThreadHandle& operator=(const ThreadHandle& handle);
operator void*() const { return m_native_handle; }
operator bool() const { return (m_native_handle != nullptr); }
/// Returns the amount of CPU time consumed by the thread, at the GetThreadTicksPerSecond() frequency.
u64 GetCPUTime() const;
/// Sets the affinity for a thread to the specified processors.
/// Obviously, only works up to 64 processors.
bool SetAffinity(u64 processor_mask) const;
protected:
void* m_native_handle = nullptr;
// We need the thread ID for affinity adjustments on Linux.
#if defined(__linux__)
unsigned int m_native_id = 0;
#endif
};
// --------------------------------------------------------------------------------------
// Thread
// --------------------------------------------------------------------------------------
// Abstracts a native thread in a lightweight manner. Provides more functionality than
// std::thread (allowing stack size adjustments).
//
class Thread : public ThreadHandle
{
public:
using EntryPoint = std::function<void()>;
Thread();
Thread(Thread&& thread);
Thread(const Thread&) = delete;
Thread(EntryPoint func);
~Thread();
ThreadHandle& operator=(Thread&& thread);
ThreadHandle& operator=(const Thread& handle) = delete;
__fi bool Joinable() const { return (m_native_handle != nullptr); }
__fi u32 GetStackSize() const { return m_stack_size; }
/// Sets the stack size for the thread. Do not call if the thread has already been started.
void SetStackSize(u32 size);
bool Start(EntryPoint func);
void Detach();
void Join();
protected:
#ifdef _WIN32
static unsigned __stdcall ThreadProc(void* param);
#else
static void* ThreadProc(void* param);
#endif
u32 m_stack_size = 0;
};
/// A semaphore that may not have a fast userspace path
/// (Used in other semaphore-based algorithms where the semaphore is just used for its thread sleep/wake ability)
class KernelSemaphore
{
#if defined(_WIN32)
void* m_sema;
#elif defined(__APPLE__)
semaphore_t m_sema;
#else
sem_t m_sema;
#endif
public:
KernelSemaphore();
~KernelSemaphore();
void Post();
void Wait();
bool TryWait();
};
/// A semaphore for notifying a work-processing thread of new work in a (separate) queue
///
/// Usage:
/// - Processing thread loops on `WaitForWork()` followed by processing all work in the queue
/// - Threads adding work first add their work to the queue, then call `NotifyOfWork()`
class WorkSema
{
/// Semaphore for sleeping the worker thread
KernelSemaphore m_sema;
/// Semaphore for sleeping thread waiting on worker queue empty
KernelSemaphore m_empty_sema;
/// Current state (see enum below)
std::atomic<s32> m_state{0};
// Expected call frequency is NotifyOfWork > WaitForWork > WaitForEmpty
// So optimize states for fast NotifyOfWork
enum
{
/* Any <-2 state: STATE_DEAD: Thread has crashed and is awaiting revival */
STATE_SPINNING = -2, ///< Worker thread is spinning waiting for work
STATE_SLEEPING = -1, ///< Worker thread is sleeping on m_sema
STATE_RUNNING_0 = 0, ///< Worker thread is processing work, but no work has been added since it last checked for new work
/* Any >0 state: STATE_RUNNING_N: Worker thread is processing work, and work has been added since it last checked for new work */
STATE_FLAG_WAITING_EMPTY = 1 << 30, ///< Flag to indicate that a thread is sleeping on m_empty_sema (can be applied to any STATE_RUNNING)
};
bool IsDead(s32 state)
{
return state < STATE_SPINNING;
}
bool IsReadyForSleep(s32 state)
{
s32 waiting_empty_cleared = state & (STATE_FLAG_WAITING_EMPTY - 1);
return waiting_empty_cleared == STATE_RUNNING_0;
}
s32 NextStateWaitForWork(s32 current)
{
s32 new_state = IsReadyForSleep(current) ? STATE_SLEEPING : STATE_RUNNING_0;
return new_state | (current & STATE_FLAG_WAITING_EMPTY); // Preserve waiting empty flag for RUNNING_N → RUNNING_0
}
public:
/// Notify the worker thread that you've added new work to its queue
void NotifyOfWork()
{
// State change:
// DEAD: Stay in DEAD (starting DEAD state is INT_MIN so we can assume we won't flip over to anything else)
// SPINNING: Change state to RUNNING. Thread will notice and process the new data
// SLEEPING: Change state to RUNNING and wake worker. Thread will wake up and process the new data.
// RUNNING_0: Change state to RUNNING_N.
// RUNNING_N: Stay in RUNNING_N
s32 old = m_state.fetch_add(2, std::memory_order_release);
if (old == STATE_SLEEPING)
m_sema.Post();
}
/// Checks if there's any work in the queue
bool CheckForWork();
/// Wait for work to be added to the queue
void WaitForWork();
/// Wait for work to be added to the queue, spinning for a bit before sleeping the thread
void WaitForWorkWithSpin();
/// Wait for the worker thread to finish processing all entries in the queue or die
/// Returns false if the thread is dead
bool WaitForEmpty();
/// Wait for the worker thread to finish processing all entries in the queue or die, spinning a bit before sleeping the thread
/// Returns false if the thread is dead
bool WaitForEmptyWithSpin();
/// Called by the worker thread to notify others of its death
/// Dead threads don't process work, and WaitForEmpty will return instantly even though there may be work in the queue
void Kill();
/// Reset the semaphore to the initial state
/// Should be called by the worker thread if it restarts after dying
void Reset();
};
/// A semaphore that definitely has a fast userspace path
class UserspaceSemaphore
{
KernelSemaphore m_sema;
std::atomic<int32_t> m_counter{0};
public:
UserspaceSemaphore() = default;
~UserspaceSemaphore() = default;
void Post()
{
if (m_counter.fetch_add(1, std::memory_order_release) < 0)
m_sema.Post();
}
void Wait()
{
if (m_counter.fetch_sub(1, std::memory_order_acquire) <= 0)
m_sema.Wait();
}
bool TryWait()
{
int32_t counter = m_counter.load(std::memory_order_relaxed);
while (counter > 0 && !m_counter.compare_exchange_weak(counter, counter - 1, std::memory_order_acquire, std::memory_order_relaxed))
;
return counter > 0;
}
};
} // namespace Threading